Demand for greater storage capacity of hard disk devices has continued to increase in recent years.
However, it has been difficult to increase the recording density of hard disk devices using existing recording systems.
Assisted magnetic recording systems are a form of technology being actively researched and focused on as next-generation recording systems. Assisted magnetic recording systems are a type of recording system in which a magnetic recording medium is irradiated with near-field light or microwaves from a magnetic head, and the coercive force in the irradiated region is locally reduced to write magnetic data therein. A magnetic recording medium which is irradiated with near-field light is referred to as a “heat-assisted magnetic recording medium”, and one which is irradiated with microwaves is referred to as a “microwave-assisted magnetic recording medium”.
In an assisted magnetic recording system, the material of which the magnetic layer is composed is a high-Ku material, such as FePt with an L10-type crystal structure (Ku up to 7×107 erg/cm3), or CoPt with an L10-type crystal structure (Ku up to 5×107 erg/cm3).
Using a high Ku material for the material composing the magnetic layer results in an increased KuV/kT. Ku is the magnetic anisotropy constant of magnetic particles, V is the volume of magnetic particles, k is the Boltzmann constant and T is the temperature. It is thus possible to minimize demagnetization by thermal fluctuation, along with the reduced volume of magnetic particles. Micronization of the magnetic particles can narrow the transition width in a heat-assisted magnetic recording system, thereby making it possible to achieve reduction in noise and improvement in the signal-to-noise ratio (SNR).
PTL 1 describes a heat-assisted data recording medium having an L10 ordered alloy layer made of a FePt alloy formed on a base layer that is composed mainly of MgO.
PTL 2 describes a heat-assisted data recording medium having a magnetic layer with an HCP structure composed of a Co-based alloy formed on a magnetic layer with an L10 structure composed of an FePt alloy, for the purpose of introducing exchange coupling between the magnetic particles of the magnetic layer with an L10 structure composed of an FePt alloy.